encapsulate access to SCC constraint graph

Author: lqd

compiler/rustc_borrowck/src/dataflow.rs

@@ -262,6 +262,9 @@ struct PoloniusOutOfScopePrecomputer<'a, 'tcx> {
 
 impl<'a, 'tcx> PoloniusOutOfScopePrecomputer<'a, 'tcx> {
     fn new(body: &'a Body<'tcx>, regioncx: &'a RegionInferenceContext<'tcx>) -> Self {
+        let sccs = regioncx.constraint_sccs();
+        let num_sccs = sccs.num_sccs();
+
         // Compute the list of SCCs that are live at all points, as it will be used for all the
         // loan scopes we'll compute.
         // FIXME: they're surely already available somewhere.
@@ -279,13 +282,12 @@ impl<'a, 'tcx> PoloniusOutOfScopePrecomputer<'a, 'tcx> {
                 );
                 live_at_all_points
             })
-            .map(|r| regioncx.constraint_sccs.scc(r))
+            .map(|r| sccs.scc(r))
             .collect();
 
         // Pre-compute the set of live SCCs per point
         let liveness = &regioncx.liveness_constraints;
-        let sccs = &regioncx.constraint_sccs;
-        let mut live_sccs_per_point = SparseBitMatrix::new(sccs.num_sccs());
+        let mut live_sccs_per_point = SparseBitMatrix::new(num_sccs);
 
         for region in liveness.rows() {
             let scc = sccs.scc(region);
@@ -306,7 +308,7 @@ impl<'a, 'tcx> PoloniusOutOfScopePrecomputer<'a, 'tcx> {
             loans_out_of_scope_at_location: FxIndexMap::default(),
             sccs_live_at_all_points,
             live_sccs_per_point,
-            reachability: BitSet::new_empty(regioncx.constraint_sccs.num_sccs()),
+            reachability: BitSet::new_empty(num_sccs),
             reachability_stack: vec![],
         }
     }
@@ -327,7 +329,7 @@ impl<'tcx> PoloniusOutOfScopePrecomputer<'_, 'tcx> {
         // regions via member constraints. (The `OutOfScopePrecomputer` wouldn't be called on a
         // region that outlives free regions via outlives constraints.)
 
-        let sccs = &self.regioncx.constraint_sccs;
+        let sccs = self.regioncx.constraint_sccs();
         let member_constraints = &self.regioncx.member_constraints;
 
         let issuing_region_scc = sccs.scc(issuing_region);

compiler/rustc_borrowck/src/region_infer/mod.rs

@@ -71,7 +71,7 @@ pub struct RegionInferenceContext<'tcx> {
     /// The SCC computed from `constraints` and the constraint
     /// graph. We have an edge from SCC A to SCC B if `A: B`. Used to
     /// compute the values of each region.
-    pub(crate) constraint_sccs: Rc<Sccs<RegionVid, ConstraintSccIndex>>,
+    constraint_sccs: Rc<Sccs<RegionVid, ConstraintSccIndex>>,
 
     /// Reverse of the SCC constraint graph --  i.e., an edge `A -> B` exists if
     /// `B: A`. This is used to compute the universal regions that are required
@@ -2279,6 +2279,11 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         }
         None
     }
+
+    /// Access to the SCC constraint graph.
+    pub(crate) fn constraint_sccs(&self) -> &Sccs<RegionVid, ConstraintSccIndex> {
+        self.constraint_sccs.as_ref()
+    }
 }
 
 impl<'tcx> RegionDefinition<'tcx> {